It is not a problem, but these are single use just emptied barrels, don't know if a sour is the way to go in one of these. Personally I would do a barley wine or imperial stout in it twice, then scrape it and re toast. After that I would use it for sours, but you could do a brown with it new, just taste often and maybe rack it out of the barrel to finish souring so you don't get too much oak.